Such regulating devices are used in internal combustion engines to regulate the gas flow to be introduced into a cylinder of an internal combustion engine with regard to its composition of recirculated exhaust gas quantities or air quantities freshly taken in. Different mixing ratios are set for reaching minimum exhaust gas values and maximum performance values depending on the operating condition of the internal combustion engine.
For regulating purposes, either two separate valves can be used, wherein a total quantity regulation via the two valves is possible, or these regulating valves comprise two valve elements which are actuated via a common actuating device so that only the mixture is changed. This configuration is in particular used in the case of turbocharged engines where the total quantity taken in can be regulated via the performance of the compressor. It is also known to use only one regulating element which cooperates with the two pipes instead of two regulating elements in order to be able to realize an even smaller configuration of the regulating device. In the case of these configurations, the exhaust gas recirculation pipe usually opens into the air intake pipe immediately downstream of the damper acting as a throttle valve. At the desired increase of the exhaust gas recirculation rate, the throttle damper is closed to the same extent to which the exhaust gas recirculation valve is opened, which results in an increase of the pressure gradient in the exhaust gas recirculation pipe besides the increase of the free cross-section of the exhaust gas recirculation pipe, whereby the fraction of the exhaust gas as compared with the air quantity taken in is increased.
Such an arrangement is described, for example, in DE 10 2012 101 851 B4 where two dampers arranged in parallel are actuated via a common rotating shaft so that, when the two dampers are rotated, the first damper is removed from the valve seat of the air intake pipe, while the second damper approaches the valve seat of the exhaust gas recirculation pipe, which is arranged perpendicularly to the valve seat of the air intake pipe, until the air intake pipe is fully opened and the exhaust gas recirculation pipe is fully closed. The valve seats for both for the second damper governing the exhaust gas recirculation pipe and for the first damper governing the air intake pipe are configured as stoppers against which the dampers fully rest in their position for closing the respective pipe. The rotating shaft is arranged at a housing wall between the opening of the exhaust gas recirculation pipe and the valve seat in the air intake pipe so that the flow is not affected by the shaft. A swirl generator is additionally arranged in the area of the opening of the exhaust gas recirculation pipe via which a swirl is impressed to the exhaust gas flow for improving mixing with the air flow.
US 2009/0283076 A1 additionally describes a damper that is arranged in an intake pipe and inside of which a pipe is formed through which exhaust gas flows that is introduced into the air flow at the damper end opposite to the shaft. While a thorough mixing of the two gas flows is attained due to this arrangement, the manufacture of the damper is laborious and the connection of the exhaust gas recirculation pipe to the inside of the damper cannot be realized in a leak-free manner. Regulation of the recirculated exhaust gas flow is not possible when this damper is used.
DE 10 2006 051 987 B4 describes a centrically mounted throttle damper on whose surface a plurality of ribs extending perpendicularly to the damper shaft are formed which serve for straightening the gas flow.
Although a good regulation of the exhaust gas recirculation system is attained with these known arrangements with costs and components being minimized, it has turned out that in particular in low-pressure exhaust gas recirculation systems, the turbulences occurring during mixing of the exhaust gas flow with the air flow affect the performance of the downstream compressor of the turbocharger or an electric compressor. Problems due to condensation may also arise if the wet exhaust gas flow is immediately directed into the cold air flow or to cold pipe walls. These condensates occurring in the gas flow may also cause damage to the compressor.